A multitude of laboratory tests for analytes of interest are performed on biological samples for diagnosis, screening, disease staging, forensic analysis, pregnancy testing, drug testing, and other reasons. While a few qualitative tests, such as pregnancy tests, have been reduced to simple kits for the patient's home use, the majority of quantitative tests still require the expertise of trained technicians in a laboratory setting using sophisticated instruments. Laboratory testing increases the cost of analysis and delays the results. In many circumstances, delay can be detrimental to a patient's condition or prognosis, such as for example the analysis of markers indicating myocardial infarction. In these critical situations and others, it would be advantageous to be able to perform such analyses at the point of care, accurately, inexpensively, and with a minimum of delay and with the assurance of the absence of a hook effect.
The hook effect, also known as a prozone effect, may arise in sandwich immunoassays when a sufficiently high concentration of a target analyte is present in the sample being tested. In particular, the high concentration of target analyte may result in substantially all of the signal antibody within the immunoassay binding to free analyte in the sample, and thus an insufficient amount of signal antibody remains to bind to analyte that is bound to the capture antibodies of the immunoassay. Consequently, a measured signal, e.g., at an immunosensor, is low, which is indicative of a small amount of analyte in the sample. However, in actuality, the analyte concentration is extremely high. The term hook effect comes from the observation that while the signal versus analyte response increases initially, e.g., in a quasi-linear fashion, the signal undesirably plateaus and then falls in a hook-like fashion.
Although a number of references disclose methods and systems for detecting the presence of the hook effect and ameliorating the affect in immunoassays, there remains a need for improved systems and methods for assuring the absence of the hook effect in immunoassays. In particular, the need remains for improved systems and methods for assuring the absence of the hook effect in immunoassay systems and methods that are intended for use outside the central laboratory, e.g., at the point of patient care. Accordingly, the need exists for ameliorating the hook effect impact on point-of-care analyte testing systems.